This is the 7922nd most frequent Russian word.
кирилла
"Кирилла" is a Russian male name, derived from "Кирилл," meaning "Cyril."
Here, 'Кирилла' is the genitive case of the proper noun 'Кирилл', used after the verb 'выбрали' (chose) to indicate selection.
Кирилла выбрали старостой класса.
Kirilla was chosen as the class leader.
Here, 'Кирилла' is again the genitive case, used to indicate a name as part of a more complex clause.
Я никогда не встречал человека по имени Кирилла.
I have never met a person named Kirilla.
In this sentence, 'Кирилле' is in the dative case of the proper noun 'Кирилл', indicating the person to whom the action 'turned' (обратилась) is directed.